Loquendo TTS is not available for Linux but there are some alternatives that runs on Linux with similar functionality. The best Linux alternative is eSpeak, which is both free and Open Source. If that doesn't suit you, our users have ranked more than 25 alternatives to Loquendo TTS and ten of them are available for Linux so hopefully you can find a suitable replacement. Other interesting Linux alternatives to Loquendo TTS are Gespeaker (Free, Open Source), Intelligent Speaker (Freemium), Fala (Free, Open Source) and Select and Speak (Paid).
Fala - A simple text reader is an open source application. A simple software that speaks a text. You can type the text or appoint a file. Fala is just a frontend to festival. Its designed for GNOME, but if you have gtk, pyhton and festival you are able to run it.
Select and Speak uses iSpeech's human-quality text-to-speech (TTS) to read any selected text in the browser. It includes many iSpeech text to speech voices in different languages. You can configure the voice and speed options by changing the settings on the options page.
KMouth is a program which enables persons that cannot speak to let their computer speak, e.g. mute people or people who have lost their voice. It has a text input field and speaks the sentences that you enter. It also has support for user defined phrasebooks.